This invention relates generally to a clean room, and more specifically to a floor for a clean room and to a method for establishing a clean room.
Clean rooms are used extensively in the electronics industry and in other industries in which a clean, particle free environment is necessary during the fabrication or testing of a product. Clean rooms are rated by the number of particles of a given standard size that are detected in a standard volume of air within the clean room. According to this rating system a xe2x80x9cClass 10xe2x80x9d clean room has only one-tenth the particle count of a xe2x80x9cClass 100xe2x80x9d clean room. Similarly, a xe2x80x9cClass 1xe2x80x9d clean room has only one-tenth the particle count of a xe2x80x9cClass 10xe2x80x9d clean room. The low particle count in a clean room is achieved by a large number of distributed air changes in the room. Air flows through the room, usually in a laminar fashion and usually downwardly from the ceiling to the floor or to vents located near the floor. The air changes wash the particulate matter from the room. Other things being equal, the greater the number of air changes, the lower the particle count in the room. For example, a xe2x80x9cClass 1xe2x80x9d clean room usually requires more than 450 air changes per hour.
Typically the air in a clean room enters the room through filters located in the ceiling, passes through the room, washing over the contents of the room, and exits the room through openings or vents in a raised clean room floor to a plenum formed between the raised floor and the structural floor of the building. The air is then recirculated and again passes through the ceiling filters and into the room.
Prior art clean rooms have all used a raised clean room floor. The raised and usually perforated clean room floor is supported on a pedestal or plurality of pedestals. The pedestals are usually specially constructed structures designed specifically for the equipment that is to be placed on the raised floor. The raised floor itself is inadequate to support the weight of the equipment. The necessary pedestal is often very expensive, sometimes having a cost equaling a large percentage of the total equipment cost. The raised floor is necessary to form the return air plenum and to provide a way to facilitate the equipment. Power lines, chemical lines, exhausts, drains, and the like pass through the raised floor and run under the raised floor to a facilities area. In addition, another reason for the widespread use of raised clean room floors, it is the desire, and often necessity, of suppressing vibrations caused by the equipment located in the clean room. Much of the processing that is done in the clean room requires a vibration free environment as well as a particle free environment. The raised floor and the platform upon which the raised floor is supported dampen vibrations that otherwise might be propagated by the underlying structural floor. A concrete slab floor has not been found satisfactory for a clean room environment because the slab tends to be a conduit for vibration.
In addition to the expense of the customized pedestal that must be used to support a raised clean room floor, there are a number of other significant drawbacks to such a floor. Because the raised floor, by itself, is unable to support the weight of equipment that might be placed in the clean room, the raised floor also cannot support the weight of that equipment as it is moved into a clean room. This results in the necessity for disassembling the raised floor when equipment is moved into a clean room or is moved about the clean room. The floor is disassembled, equipment is moved into the clean room, placed on the portion of the raised floor in substantially its final location, and then the remaining portion of the raised floor is reassembled. This activity compromises the cleanliness of the clean room every time a piece of equipment is moved into or is moved about the clean room. In addition, any facilities lines that would be located under the portion of the raised floor that has to be removed will also be disturbed by the moving of equipment. Because of these difficulties, it is commonplace to build relatively small or compartmentalized clean rooms so that only a small area is contaminated by any moving process. This, of course, leads to disadvantages in terms of material flow because materials being processed must be moved into and out of these individual compartmentalized clean rooms.
In view of these and other problems with conventional clean room designs, it has been recognized that a need exists for a clean room that is less expensive than a raised floor clean room. There is also a need for a clean room that allows for non-intrusive clean room practices for facilitizing equipment located in the clean room. The need also exists for a clean room that does not require an expensive and customized pedestal for equipment, but rather allows the placement of equipment anywhere within a clean room. There is also a need for a clean room into which equipment can be moved and relocated without compromising the integrity of the clean room. A need also exists for a clean room that can be large in area and arbitrarily expandable in area.
In accordance with one embodiment of the invention, a clean room is provided having a bearing floor capable of supporting equipment in any location thereon. The bearing floor is positioned over a facilities room which, in effect, is an extension of the clean room. The bearing floor has a regular array of openings through the floor which permit air to flow from the clean room into the underlying facilities room. A wall structure is positioned on the bearing floor to surround a selected area of the bearing floor. A ceiling having a plurality of filtered air inlets is provided above the bearing floor and in contact with the top of the wall structure. A plurality of grates are positioned in those floor openings of the regular array that are located within the selected area bounded by the walls and solid, air impervious members are positioned in those floor openings of the regular array that are located outside the selected area. By changing air impervious members for grates, or vice versa, the area of the clean room can be expanded or reduced. Preferably the location and number of filtered air inlets is also adjusted to correspond to the number of grated openings in the clean room floor.